A high throughput drug screen based on fluorescence resonance energy transfer (FRET) for anticancer activity of compounds from herbal medicine

Background and purpose: We report the development of a very efficient cell-based high throughput screening (HTS) method, which utilizes a novel bio-sensor that selectively detects apoptosis based on the fluorescence resonance energy transfer (FRET) technique.Experimental approach: We generated a stable HeLa cell line expressing a FRET-based bio-sensor protein. When cells undergo apoptosis, they activate a protease called “caspase-3”. Activation of this enzyme will cleave our sensor protein and cause its fluorescence emission to shift from a wavelength of 535 nm (green) to 486 nm (blue). A lowering of the green/blue emission ratio thus gives a direct indication of apoptosis. The sensor cells can be grown in 96-well plates. After adding different chemical compounds to each well, the fluorescent profile can be measured at various times using a fluorescent plate reader. Compounds that can trigger apoptosis are potential candidates of anti-cancer drugs. Key results: We demonstrated that this novel cell-based HTS method is highly effective in identifying anti-cancer compounds. First, this system is very sensitive in detecting apoptosis induced by various known anti-cancer drugs. Second, this system detects only apoptosis but not necrosis, and thus is more useful than the conventional cell viability (such as MTT) assays. Finally, we have used this system to screen compounds isolated from two herbal plants used in Chinese medicine, and identified several effective compounds for inducing apoptosis. Conclusions and Implications: This FRET-based HTS method is a powerful tool for identifying anti-cancer compounds and can serve as a highly efficient platform for drug discovery.